US3405353A - Magnetic thickness gauge using simultaneous constant and ac magnetization - Google Patents

Magnetic thickness gauge using simultaneous constant and ac magnetization Download PDF

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Publication number
US3405353A
US3405353A US545202A US54520266A US3405353A US 3405353 A US3405353 A US 3405353A US 545202 A US545202 A US 545202A US 54520266 A US54520266 A US 54520266A US 3405353 A US3405353 A US 3405353A
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United States
Prior art keywords
flux
sheet
thickness
core
yoke assembly
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Expired - Lifetime
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US545202A
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English (en)
Inventor
Smith Terence Princep
Lack Keith Malcolm
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Teledictor Ltd
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Teledictor Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
    • G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
    • G01B7/10—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance

Definitions

  • This invention has reference to apparatus for measuring the thickness of sheets of ferromagnetic materials and is concerned more particularly although not specifically with apparatus for measuring or gauging and indicating visually the thickness of tinplate sheets having a thickness in the range of 0.006" to 0.024".
  • the invention has for its primary objective to provide apparatus for measuring the thickness of tinplate sheets of the order of thickness aforesaid which is substantially instantaneous in action and which affords a visual indication of thickness on a calibrated scale with a high degree of discrimination between the various thicknesses graduated on the scale.
  • the invention is based on the principle that if sufficient magnetic flux is passed through a sheet under test to saturate the material magnetically completely and the saturation flux density of the sheet under test is maintained substantially constant the total flux passing through the sheet is a function only of the area of the flux path, which, if the remainder of the magnetic circuit is kept constant, is proportional to the sheet thickness.
  • the invention consists of apparatus for measuring the thickness of sheets of ferromagnetic material
  • a sensing head consisting of a permanent magnet or electromagnet powerful enough either directly or indirectly through an interposed flux responsive memher to saturate magnetically the thickest sheet to be tested and on which permanent magnet or electromagnet or liux responsive member the sheet to be tested is required to be rested
  • a flux plate on which the said permanent magnet or said electromagnet is mounted and which is large enough to carry the total flux produced by the said permanent magnet or said electromagnet
  • a laminated yoke assembly adapted to rest on the flux plate and to contact with the underside of the sheet to be tested when placed on the permanent magnet or electromagnet aforesaid or on the flux responsive member and which laminated yoke assembly is in magnetic circuit with the said permanent magnet or said electromagnet and flux plate, the areas of the said flux plate and laminated yoke assembly being large enough to remain unsaturated when the magnetic circuit is completed by the thickest sheet to be tested, a
  • the invention also resides in apparatus for measuring the thickness of sheets of ferromagnetic material constructed, arranged and adapted for use substantially as will be described hereinafter.
  • FIGURE 1 is a diagrammatic view illustrating separated the three essential component units of the apparatus.
  • FIGURE 2 is a perspective view of the apparatus as available in commerce.
  • FIGURE 3 is a longitudinal section on an enlarged scale of the forepart of the apparatus as illustrated in FIG- URE 2.
  • FIGURE 4 is a plan of the sensing head as incorporated in the forepart of the apparatus illustrated in FIGURE 3.
  • FIGURE 5 is a View on an enlarged scale partly in longitudinal section and partly in elevation of the rear portion of the apparatus as illustrated in FIGURE 2.
  • the apparatus consists of three units, namely:
  • a sensing head designated generically by the reference letter A,
  • An amplifier unit designated generically by the reference letter B
  • a display device based on a cathode ray tube designated generically by the reference letter C.
  • the sensing head A aforesaid consists of a permanent ring magnet 10 which is powerful enough to saturate the thickest sheet to be tested for thickness, a lower flux plate 11 on which the ring magnet 10 rests and which is large enough to carry the total flux produced by the said ring magnet 10 without magnetically saturating a laminated yoke assembly 12 of thin sheet steel stampings of known formation.
  • This laminated yoke assembly 12 rests on the central portion of the flux plate 11 and projects through the hole 101 in the ring magnet 10 but with a clearance between the sides and ends of the said laminated yoke assembly 12 and the inner periphery of the ring magnet 10, see FIGURE 4.
  • annular flux sleeve 13 Superposed on the ring magnet 10 and in magnetic contact therewith is an annular flux sleeve 13 the upper surface of which is on the same plane as the top of the laminated yoke assembly 12 when rested on the flux plate 11 and which surfaces are contacted by the underside of the sheet D the thickness of which is to be ascertained when the said sheet D is rested on top of the said flux sleeve 13 and the top of the laminated yoke assembly 12.
  • Wound around the laminated yoke assembly 12 is a search coil 121.
  • the flux sleeve 13 and the laminated yoke assembly 12 are so arranged that the sheet D under test is in intimate contact with the whole of the area presented to it by the presented surface of the flux sleeve 13 and of the laminated yoke assembly 12 so that there will be a flux in the laminated yoke assembly 12 which is proportional to the thickness of the sheet D to be tested according to the basic principle hereinbefore stated.
  • the amplifier unit B incorporates a resistance 141 of low value which is connected in series with the search coil 121 and in parallel with an amplifier 14 of known construction which is designed so as to amplify only unidirectional half-cycles of an alternating electric current and to reject the unwanted half-cycle.
  • the display device C comprises a relatively large cathode ray tube 15 with which is associated settable magnetic means 151 for causing the electron beam in known manner to be deflected towards one end of the cathode ray tube 15 to constitute the starting point for collaboration with a calibrated scale 16 on a screen 161- placed over the cathode ray tube 15 and which scale 16 runs diagonally from a position in front of the said startin point 0 upwardly to the other end L of the scale 16.
  • the said scale 16 is graduated in terms of thicknesses within the limits of the range proposed for the apparatus and bounds one side of a slot 162 in the screen 161.
  • the spot of the cathode ray tube 15 is caused to be visible through an inclined slot 162 of the screen 161 the lower marginal edge of which is calibrated as at 163 in terms of thickness.
  • the sensing head A is housed within a separately formed detachable sheet metal housing A1, see FIGURES 2 and 3, with the upper end of the said sensing head located in a cut-out in the inclined top surface All of the said housing A1 with the upper end of the sensing head A in the same plane as the inclined top surface A11.
  • the inclined surface A11 serves as the support for the sheet D being tested at any one time.
  • the cathode ray tube, amplifier unit and other components of the display device are mounted in or on a separately formed detachable sheet metal housing B1 which in turn is bolted to a sub-posed separately formed detachable sheet metal base housing B2.
  • the base housing B2 with the sub-posed housing B1 is bolted end to end with the housing Al, the two ends of the housings A1 and B2 carrying the complementary connector components for the lead 122.
  • the tinplate sheet D In use the tinplate sheet D the thickness of which is to be ascertained is placed in intimate contact with the upper surface of the flux sleeve 13 and the top of the laminated yoke assembly 12 in magnetic circuit therewith and thus with the ring magnet and fiux plate 11 whereupon alternating EMF is app-lied to the search coil 121 and since the magnetic flux in the laminated yoke assembly 12 is produced by the permanent ring magnet 10, the flux is unidirectional and hence the amplitude of the alternating current will differ between positive and negative half-cycles depending upon whether the alternating ampere turns produced by the search coil 121 add or subtract from the unidirectional flux.
  • the current passing through the search coil 121 is fed by way of the resistance 141 of low value and produces a voltage pulse proportionate to the current which is fed to the amplifier unit 14 so that the output of the said amplifier unit 14 consists of a series of pulses which repeat every half-cycle of the alternating EMF and have an amplitude proportional to the thickness of the sheet D being tested and which are at a power level compatible with the drive requirements of the scanning coils of the relatively large cathode ray tube 15.
  • the response time of the apparatus is virtually instantaneous.
  • the whole of the space surrounding the said laminated yoke assembly 12 is filled with a non-conducting synthetic plastics material 17, preferably a polyester resin, which is cured in situ.
  • the laminated yoke assembly 12 may be wound with more than one search coil 121.
  • an electromagnet may be used in place of a permanent magnet.
  • Apparatus for measuring the thickness of sheets of ferromagnetic material comprising a measuring head incorporating:
  • (h) means connected across said load and conductive winding for applying an alternating electromotive force to said winding sufiicient when the core is biased in a forward direction by magnetic flux from said magnet flowing through said magnetic circuit and said sheet of ferromagnetic material, to drive the core to saturation in a forward direction but not sufficient to drive said core to saturation in a reverse direction,
  • (j) means for displaying the amplitude of the voltage pulse across the load as a measure of the current pulse through said load at saturation and thus as a measure of thickness of the sheet of ferromagnetic material.
  • the elements of ferromagnetic material of said magnetic circuit including a flux plate on which said ring magnet is mounted and a flux sleeve surrounding the core and extending from the flux plate to form one of said poles, said core extending from the flux plate and forming said other pole.
  • the elements of ferromagnetic material of said magnetic circuit including a flux plate on which said ring magnet is mounted and a flux sleeve surrounding the core and extending from the flux plate to form one of said poles, said core extending from the flux plate and forming said other pole and said flux sleeve being filled with synthetic resin.
  • said means for displaying the amplitude of the voltage pulse incorporating a cathode ray tube.
  • Apparatus according to claim 1 including a housing within which said measuring head is mounted, said housing having a flat upper face and the poles of the measuring head being flush with said upper face whereby the face provides support for a sheet to be measured.
  • the elements of ferromagnetic material of said magnetic circuit including a flux plate on which said ring magnet is mounted and a flux sleeve surrounding the core and extending from the flux plate to form one of said poles, said core extending from the flux plate and forming said other pole, and also including a housing in which the measuring head is mounted, said housing having a flat upper face and the poles of the measuring head being flush with said upper face whereby the face provides support for a sheet to be measured.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Measuring Magnetic Variables (AREA)
US545202A 1965-07-21 1966-04-06 Magnetic thickness gauge using simultaneous constant and ac magnetization Expired - Lifetime US3405353A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB30990/65A GB1097179A (en) 1965-07-21 1965-07-21 Apparatus for measuring the thickness of sheets of ferromagnetic materials

Publications (1)

Publication Number Publication Date
US3405353A true US3405353A (en) 1968-10-08

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Family Applications (1)

Application Number Title Priority Date Filing Date
US545202A Expired - Lifetime US3405353A (en) 1965-07-21 1966-04-06 Magnetic thickness gauge using simultaneous constant and ac magnetization

Country Status (7)

Country Link
US (1) US3405353A (de)
BE (1) BE679673A (de)
DE (1) DE1548329A1 (de)
ES (1) ES325642A1 (de)
GB (1) GB1097179A (de)
LU (1) LU51134A1 (de)
NL (1) NL6607104A (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3922599A (en) * 1973-09-12 1975-11-25 Nix Steingroeve Elektro Physik A.C. electromagnetic thickness gauge utilizing premagnetization of the gauge core to render sensitivity independent of thickness
US4553095A (en) * 1982-06-10 1985-11-12 Westinghouse Electric Corp. Eddy current thickness gauge with constant magnetic bias
US4618823A (en) * 1982-09-30 1986-10-21 Werner Turck Gmbh & Co. Kg Inductive proximity switch having an oscillator magnetic core and a permanent magnet forming a saturation-sensitive magnetization area
US5283520A (en) * 1991-04-04 1994-02-01 Martin Philip W Method of determining thickness of magnetic pipe by measuring the time it takes the pipe to reach magnetic saturation
US6529008B1 (en) * 1998-04-27 2003-03-04 Moustafa Abdel Kader Mohamed Electromagnetic induction coil sensor
CN108639754A (zh) * 2018-05-21 2018-10-12 安徽安元智能科技有限公司 用于厚度测量机的取料装置的取料方法
RU2752353C1 (ru) * 2020-09-03 2021-07-26 Федеральное государственное бюджетное образовательное учреждение высшего образования Иркутский государственный университет путей сообщения (ФГБОУ ВО ИрГУПС) Способ определения оптимальной толщины листов магнитопровода трансформатора

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9702106D0 (en) * 1997-02-01 1997-03-26 British Steel Plc Saturation magnetisation measurements
US20100171493A1 (en) * 2009-01-07 2010-07-08 Robert Standen Method and device for measuring thickness of a substrate

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB599601A (en) * 1945-10-12 1948-03-16 Birmingham Small Arms Co Ltd Improvements relating to means for measuring the thickness of non-magnetic coatings on magnetic bases
US2733358A (en) * 1956-01-31 Signal
US2935680A (en) * 1953-09-10 1960-05-03 Continental Can Co Means of gauging sheet metal and the like

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2733358A (en) * 1956-01-31 Signal
GB599601A (en) * 1945-10-12 1948-03-16 Birmingham Small Arms Co Ltd Improvements relating to means for measuring the thickness of non-magnetic coatings on magnetic bases
US2935680A (en) * 1953-09-10 1960-05-03 Continental Can Co Means of gauging sheet metal and the like

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3922599A (en) * 1973-09-12 1975-11-25 Nix Steingroeve Elektro Physik A.C. electromagnetic thickness gauge utilizing premagnetization of the gauge core to render sensitivity independent of thickness
US4553095A (en) * 1982-06-10 1985-11-12 Westinghouse Electric Corp. Eddy current thickness gauge with constant magnetic bias
US4618823A (en) * 1982-09-30 1986-10-21 Werner Turck Gmbh & Co. Kg Inductive proximity switch having an oscillator magnetic core and a permanent magnet forming a saturation-sensitive magnetization area
US5283520A (en) * 1991-04-04 1994-02-01 Martin Philip W Method of determining thickness of magnetic pipe by measuring the time it takes the pipe to reach magnetic saturation
US5426367A (en) * 1991-04-04 1995-06-20 Martin; Philip W. Logging of cased well by induction logging to plot an induction log of the well
US6529008B1 (en) * 1998-04-27 2003-03-04 Moustafa Abdel Kader Mohamed Electromagnetic induction coil sensor
CN108639754A (zh) * 2018-05-21 2018-10-12 安徽安元智能科技有限公司 用于厚度测量机的取料装置的取料方法
CN108639754B (zh) * 2018-05-21 2019-05-10 安徽安元智能科技有限公司 用于厚度测量机的取料装置的取料方法
RU2752353C1 (ru) * 2020-09-03 2021-07-26 Федеральное государственное бюджетное образовательное учреждение высшего образования Иркутский государственный университет путей сообщения (ФГБОУ ВО ИрГУПС) Способ определения оптимальной толщины листов магнитопровода трансформатора

Also Published As

Publication number Publication date
GB1097179A (en) 1967-12-29
BE679673A (de) 1966-10-03
NL6607104A (de) 1967-01-23
LU51134A1 (de) 1966-07-18
ES325642A1 (es) 1967-02-16
DE1548329A1 (de) 1969-08-21

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